Question

Which type of cell junction helps to stop substances from leaking across a tissue?

Answer 1

Specialized cell junctions occur at points of cell-cell and cell-matrix contact in all tissues, and they are particularly plentiful in epithelia. Cell junctions are best visualized using either conventional or freeze-fracture electron microscopy(discussed in Chapter 9), which reveals that the interacting plasma membranes (and often the underlying cytoplasm and the intervening intercellular space as well) are highly specialized in these regions.

Cell junctions can be classified into three functional groups:

1.

Occluding junctions seal cells together in an epithelium in a way that prevents even small molecules from leaking from one side of the sheet to the other.

2.

Anchoring junctions mechanically attach cells (and their cytoskeletons) to their neighbors or to the extracellular matrix.

3.

Communicating junctions mediate the passage of chemical or electrical signals from one interacting cell to its partner.

Answer 2

Hello Mate,

In many animal tissues (e.g., connective tissue), each cell is separated from the next by an extracellular coating or matrix. However, in some tissues (e.g., epithelia), the plasma membranes of adjacent cells are pressed together. Four kinds of junctions occur in vertebrates: Tight junctions